1. Field of the Invention
The present invention relates to a recording/reproducing tape cassette attached with a lid and more particularly to improvements in the lid spring used for the lid capable of rotatably clamping the upper and rear surfaces of the exposed portion of the tape and the lid spring engagement portion.
The present invention further relates to an improvement in a lid mechanism for a recording/reproducing tape cassette for the purpose of smoothing the opening and closing operations of the lid and more particularly, to a tape cassette structure having a lid which is made to open and close quickly by suitably setting the position of an elastic member guide portion located close to a tape end detecting optical path for detecting the amount of tape so that the force of the elastic member becomes variable.
2. Description of the Related Art
A prior art recording/reproducing tape cassette 60 attached with a lid comprises a substantially square front shell 2, a reel portion 5 comprised of a pair of reels 4 around which a tape 3 is wound, a lid mechanism 61 including a rotatable lid for clamping the upper and rear surfaces of a part of the tape exposed outside the cassette 60 and a substantially square lower shell 37 capable of engaging the upper shell, as shown in FIG. 9.
As shown in FIG. 9, the upper shell 2 is formed of a substantially square insulating member and is provided with a pair of top-lid guide grooves 7, respectively, which are formed on both longitudinal side surfaces thereof so as to extend rearwardly from the front surface, a pair of front-lid rotating shaft bearing portions 8, a pair of tubular lower shell engagement projections 9 and a back-lid engagement portion 10 of a predetermined length formed by recessing the central portion of the front edge of the upper shell 2.
The lid mechanism 61 comprises a top-lid 12, a back-lid 17, a front-lid 21 and a lid spring 65 in the form of an elastic torsion coil spring. The lid mechanism 61 operates such that when the cassette 60 is in use, it leaves away from the tape 3 as it opens to release the tape clamped thereby.
As shown in FIG. 9, the top-lid 12 is rectangular and comprises two longitudinal side walls 13, a pair of front-lid engagement holes 14 formed inside the side walls 13 in opposite relationship with each other with each being in the form of a partly recessed blind hole, a pair of upper shell engagement projections 15 respectively formed on the side walls 13 at positions behind the front-lid engagement holes 14 so as to be guided by the top-lid guide grooves 7 and a pair of back-lid engagement projections 16 formed on the inner surface of the top-lid 12 in spaced apart relationship with each other inwardly of the side walls 13 so as to engage the back-lid 17.
As shown in FIG. 9, the back-lid 17 has a horizontally elongated triangular lower portion and an elongated platelike tape retaining surface 18A for clamping the exposed portion of the tape 3. Further, one side surface of the triangular lower portion of the back-lid 17 is provided with a lower shell guide projection 19 interlocking with the tape clamping and unclamping operations and the upper end of the tape retaining surface 18A is provided at both ends thereof with a pair of top-lid engagement projections 20.
As shown in FIG. 9, the front-lid 21 comprises an elongated flat base plate portion 22, a pair of front-lid retaining portions 23 extending from both ends of the base plate portion 22 in a direction intersecting the longitudinal direction of the latter, a pair of top-lid engagement projections 20A to engage the top-lid 12 and a tape retaining surface 18B formed on the rear side of the base plate portion 22 so as to clamp the tape.
The front-lid retaining portions 23 are provided with lid-rotating shafts 62 and 35, respectively, which are different in structure and which face each other inwardly right and left and are also provided with tongue-like lid-engagement pieces 26 at positions near the free ends thereof, respectively.
As shown in FIGS. 10 and 11, the lid rotating shaft bearing portion 62 (see the leftside of FIG. 9) is an engagement portion for the lid mechanism 6 and comprises a axial portion 27 rotatably engageable with a front-lid rotating shaft bearing portion 8 and a front-lid engagement portion 41, a support shaft 63 coaxial with the axial portion 27 for mounting a lid spring 65 thereon and a flange portion 64 of an enlarged diameter provided between the axial portion 27 and the support shaft 63.
The support shaft 63 has a diameter smaller than the inner diameter of an end turn 66 of the lid spring 65 and is provided with a hook engagement portion 64 projecting from a portion of the support shaft 63 in a direction intersecting at right angles with the axis of the support shaft 63.
As shown in FIGS. 12 and 13, the lid spring 65 may comprise the end turn 66 wound in the form of a torsion coil spring, an arm portion 67 formed by linearly expanding one end of the end turn 66 and a semi-circular hook portion 66 formed by raising the end turn portion 66 of a diameter Dc upward by 90.degree.. In that case, the distance between the end turn portion 66 and the free end of the hook portion 68 is dc and it is therefore necessary to increase the width wa for accommodating the lid spring 65 shown in FIG. 10.
Therefore, as shown in FIG. 13, the hook portion 69 is made to have a limited height Y in such a manner that after a wire having an end turn is raised upward by 90.degree., the wire is reprocessed to reduce the diameter dh of the semi-circular portion of the wire. Thus, the width wb can be increased to allow the lid spring 65 to be mounted on the front-lid rotating shaft bearing portion 8 support shaft 63.
The lid rotating shaft 35 (the right side in FIG. 9) comprises a shaft 36 rotatably engageable with the front-lid rotating shaft bearing portion 8 of the upper shell 2 and the front-lid rotating shaft engagement portion 41 of the lower shell 37.
As shown in FIG. 9, the lower shell 37 is substantially square in shape so as to engage the upper shell 2 and is provided with a pair of lid engagement portions 40 on both shorter sides thereof.
The assembly of the tape cassette 60 having a lid comprising the various kinds of parts described above is performed in such a manner that the pair of reels 4 having the tape wound therearound are first mounted in the lower shell 37, then the back-lid 17, the top-lid 12 and the front-lid 21 are brought into engagement with one another and then with the upper shell 2 and the lid spring 65 is fitted on the support shaft 63 to thereby complete the lid mechanism 61. Then the lid mechanism 61 is placed over the lower shell 37 while it is kept opened against the force of the lid spring 65 to thereby complete the assembly of the cassette 60.
Further, as shown in FIG. 21, a prior art recording/reproducing cassette with a lid is provided with a lid mechanism comprising, in combination, a top lid 118, a front lid 109 and a back lid 115 and provided on the front surface of a combined structure of an upper shell 102A and a lower shell 102B.
These lids 118, 109 and 115 are made to open and close in interlocking relationships with one another as they are guided by grooves formed in the shells 102A and 102B such that when the cassette 1 is not in use, the tape is protected by being clamped between a front lid 109 and a back lid 115 while when the cassette 1 is in use, the lids move upward as they release the tape from its clamped state allowing a part of the tape to become exposed outside completely.
The closing operation of the lids 118, 109 and 115 is effected by the elastic force of a torsion coil spring 121 fitted on a guide portion 114A coaxial with a lid rotating shaft 113A of the lid mechanism.
Further, the position of the guide portion 114A is close to a tape end detecting optical path 122 and usually it is substantially the same size as the lid rotating shaft 113A for rotating the lid mechanism. Further, the distance between the guide portion 114A and the tape end detecting optical path 122 is, as shown in FIG. 21, is formed to a size such that when the torsion coil spring 121 is mounted, the end of the spring 121 does not block at lease the tape end detecting optical path 122. Accordingly, the torsion coil spring 121 is made to have a predetermined outer diameter.
As prior art cassette techniques, the following three patent applications are proposed by the present applicant.
1. U.S. Pat. No. 4,989,111 PA0 2. U.S. Pat. No. 5,024,394 PA0 3. Japanese Patent Application No. H05010347
(Note: Each of the above applications is owned by the assignee of the present invention and is hereby incorporated by reference.)